In the context of improving the performances of its tires, the applicant company has filed several patents in which various geometries of incisions are described which, while creating additional ridges which are indispensable for cutting the film of water covering the roadway, make it possible to limit the loss of rigidity of the tread due to the presence of these incisions. For example, U.S. Pat. No. 4,794,965 describes a specific arrangement of incisions in a zigzag within the thickness of a tread; U.S. Pat. No. 5,783,002 describes an incision the opposing walls of which are provided with motifs in relief intended to fit into one another when passing into the imprint with the roadway. These various incisions ensure mechanical cooperation of the walls of rubber mix which is very appreciable for reducing the relative movements between said walls.
The development of vehicles using new driving aid systems (wheel anti-locking system when braking, anti-skid system, stability control system) mean that the requirements in terms of the performance of tires have changed.
For these vehicles, there has been discovered a need for a tire having a tread provided with a plurality of incisions to form a plurality of ridges intended to come into contact with the roadway, these incisions having a new geometry which, while limiting the reduction in overall rigidity of this tread under high shearing stresses, has the ability to reduce as far as possible the relative movements between the opposed walls once they are in at least partial contact with each other under low shearing stresses (and very particularly in rainy weather or when the roadway is wet).
In the known prior art, there are documents which state the advantage of producing on the walls of the incisions areas of roughness having specific dimensions. For example, the Japanese document published under the number 96/175115 advocates a roughness of between 20 and 300 microns.
However, it was demonstrated that merely these areas of roughness were insufficient to achieve a good compromise under all conditions of use of these tires.